Pressurized systems, including pressure vessels, piping, and other systems are often equipped with pressure relief devices to protect systems from overpressure conditions. Overpressure conditions can arise from a process error, instrument or equipment failure, fire, or other malfunction, which causes the pressure of the fluid in the system to increase above predefined parameters. As used herein, the term fluid may encompass liquid, vapor, gas, or a mixture of any of these fluid phases. Pressure relief devices may include a variety of different types, sizes, and configurations. For example, pressure relief devices can be self-actuated in that the device detects an overpressure condition and opens to release excess pressure from the system. In some cases, pressure relief devices are set to remain closed at a particular pressure setting. When the internal pressure of the line exceeds the predefined pressure setting, the pressure device can be forced open by the internal pressure, allowing excess pressure to escape the relief device. When the internal pressure of the lines and/or vessels of the system normalizes or otherwise returns to an acceptable level, the pressure relief device can return to its closed, sealed state, until the next overpressure state is reached and/or detected. A number of pressure relief devices are known in the art. Pressure relief devices, or pressure safety valves, can include, but are not limited to pilot-operated relief valves, spring-, electromagnetic-, and pneumatic-driven valves.
Pressure relief devices can be monitored to indicate the occurrence of overpressure conditions within a system. Additionally, monitoring systems have been employed to monitor the performance of pressure relief devices themselves. Typical monitoring systems employ position sensors, such as position transducers, to detect movement within the pressure relief device, indicating that the seat of the device has been displaced and the valve opened. Other monitoring devices in the art employ ultrasonic devices for detecting sounds and vibrations associated with the release of fluid from the relief device as well as the mechanical opening of the valve.